Cracks spreading prognostication method for concrete and reinforced concrete elements

Abstract The rupture cracks development, brittle failure and design improvement for preventation the brittle failure of concrete elements are considered. The demerits of known Fracture Mechanics (FM) models are noted and for overcoming of the ones the peculiar FM model is offered, based on modelling the stress distribution only along the crack Fracture Process Zone (FPZ) with the elastic material behavior out of the FPZ. This specific stress distribution was called “Physically Verisimilar Stresses (PVS)”, are the one is accepted as basis of the being offered new FM model, which uses three material parameters: maximal stress σ m , intra-structural linear size “a” and dimensionless value “n”, taking into account the plastic properties of material. Strength problems are solved by the “Modified Method of Sections (MMS)”, in which the PVS is applied along the FPZ. The FM model on the basis PVS and MMS leads to acceptable in practice method of strength design the elements with cracks. The offered PVS model and MMS allow to predict the cracks development with consideration as their initial stable growing up to the critical values of crack length and load, as unstable crack propagation. The paper states examples of designs and shows sufficient nearness of the theoretic strength to the experimental one.